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A fish rising up vertically toward the surface of water with speed `3ms^(-1)` observes a bird diving down vertically towards it with speed `9ms^(-1)` . The actual velocity of bird is

A

`6m//sec`

B

`4m//sec`

C

`3.5m//sec`

D

`4.5m//sec`

Text Solution

Verified by Experts

The correct Answer is:
D

Distance between bird and fish, as seen by fish
`s=x+muy`
`(ds)/(dt)=(dx)/(dt)+mu(dy)/(dt)`
`9=3+4/3*(dy)/(dt)`
`(dy)/(dt)=18/4=4.5m//sec`
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CP SINGH-REFRACTION OF LIGHT BY PLANE SURFACES-Exercises
  1. A bird flies down vertically towards a water surface. To a fish inside...

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  2. A ball is dropped from a height of 20m above the surface of water in a...

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  3. A fish rising up vertically toward the surface of water with speed 3m...

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  4. P is a point on the axis of a concave mirror. The image of P, formed b...

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  5. A vessel of depth d is half filled with a liquid of refractive index m...

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  6. A plane mirror is placed at the bottom of a tank containing a liquid o...

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  7. An object is placed 20cm in front of a block of glass 10cm thick havin...

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  8. A slab of glass of refractive index 1.5 and thickness 3cm is placed wi...

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  9. A microscope is focused on a mark on a piece of paper and then a slab ...

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  10. A container is filled with water (mu=1.33) upto a height of 33.25 cm. ...

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  11. A diverging beam of light from a point source S having devergence angl...

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  12. A concave mirror is placed at the bottom of an empty tank with face up...

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  13. A pile driven into the bottom of a lake extends 3m above the bottom of...

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  14. A concave mirror with its optic axis vertical and mirror facinig upwar...

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  15. The mean distance of sun from the earth is 1.5xx10^8km. The time taken...

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  16. A ray of light composed of blue and red light is incident on a paralle...

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  17. When a ray of light enters a water filled glass tank from a glass face...

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  18. Light passes through a glass slab with parallel sides and thickness t....

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  19. A ray of light is incident on a surface of glass slab at an angle 45^@...

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  20. Two transparent slabs have the same thickness as shown in figure. One ...

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